Two-flame arc lamp



March 12,1929. E, J, S HAUB' 1,704,904

TWO-FLAME ARC LAMP Original Filed Aug 14. 1920 5 s t -s t 1 INVENTOR 1 ATTO NEY5 March 12, 1929. E J, HA B 1,704,904

TWO-FLAME ARC LAMP I Original Filed Aug. 14. 1920 5 s t -s t 2 INVENTOR A4, 6,2 rj

ATTORNEYY.

March 12, 1929. sc -{Aug 1,704,904

TWO-FLAME ARC LAMP Original Filed Aug. 14 1920 3 sheets-sheet 3 ATTORNEYJT preferably Patented Mar. 12, 1929.

UNITED STATES EUGENE J. SGHAUB, OF MASPETH, NEW YORK.

TWO-FLAME ARC LAMP.

Application filed August 14, 1920, Serial No. 403,545. Renewed June 7, 1928-.

This invention relates to electric arcs. More specifically it relates to flaming arcs particularly adapted for picture projection and has for one of its principal objects to provide a method of operating such arcs at high efficiency and an apparatus for practising such method. Other objects and advantages will appear as the invention is hereinafter disclosed.

Referring to the drawings which illustrate what ll now consider preferred physical embodiments of my invention:

Fig. 1 is a fragmentary detail view illustrating an are operated in accordance with my invention. a

Fig. 2 is an end elevation of the device illustrated in Fig. 1.

Fig. 3 is a somewhat diagrammatic view of my invention as applied to picture projection. 1

Fig. 4 is an elevation, partly in section and with parts broken away, of a preferred form of control and operating mechanism.

Fig. 5 is a detail end elevation showing a part of the structure illustrated in Fig. 4.

Fig. 6 is a wiring diagram.

Calling attention to Figs. 1 and 2, it will be seen that l have shown an are formed between two electrodes 1 and 2. The positive carbon or electrode is cored, i. e., provided with a substantially central or axial bore 3, which contains a core 1, consisting of a mixture of metallic salts and pulverized carbon or graphite, in suitable proportions for the current density used, which when subjected tothe heat of the arc emits a very brilliant VZLPOFOJE high electrical conductivity. Such electrodes are now well known in the art,

being at this time employed in A. C. white flame arcs for picture projection and also in flaming arcs for photo-engraving purposes, and therefore need no more detailed description ,than that above indicated. The negative carbon or electrode 2 is also provided with a bore 5 anda core 6 of are sustaining material. This type of electrode is also well known in the art, it being the kind now generally used for picture projection arcs of'the ordinary type. It will be noted that the axis of the negative electrode 2 makes an angle of 65 with the axis of the positive 3-, and although this anglev may be varied it is between the limits of and 95. Some of the more important characteristics of my'invention may be set forth by explaining certain observations made in operating an are between electrodes arranged and constructed such as those above de scribed, and having substantially the follow ing dimensions: positiveexternal diameter 5/8 inch, positive core diameter 11/6d inch, and negative external diameter 3/8 inch. A direct current source of such potential as to maintain a current of about amperes through the arc was connected across the electrodes 1 and 2 and the tips of the electrodes momentarily touched or brought into contact with each other, and then separated by moving the negative away from the posi; tive to a distance of about 1/2 inch. When separation occured an arc was established between the electrodes 1 and 2, the negative flame conducting the current directly to the positive carbon as occurs in the ordinary and Well known carbon are. In a short time, about the order of three seconds, the positive carbon shell became hot enough to heat the core to a temperature at which the core started to emit hlghly electrically conductive vapors. For a short time, about the order of five or six seconds, the arc sputtered and hissed as the negative flame would jump from the shell to the positive vapor stream for an instant and then back to the shell again. The negative flame thus intermittently making connection, electrically, with the positive vapor stream further raised its temperature and that of the core until a point was reached where the electrical conductivity of the positive vapor stream became great enough to shunt practically all of the current awayl from the shell when the are settled down and burned quietly with the negative flame deflected away from the positive crater .face. Thearc then assumed the appearance indicated in Fig. 1. A comparatively wide crater or moderate depth and conical in shape quickly formed at the active end of the positive electrode and the tip of the latter rounded ofi evenly at 8 as the positive rotated or turned. The negative flame 9 had no tongue and did not touch the positive electrode 1 but was kept therefrom'by the vapor blast from the positive crater which issued in a manner similar to the discharge of steam under pressure from a nozzle. The negative flame 9 met the positive flame 10 at a point 11 spaced from the positive crater face a distance of the order of about 1/4 inch. An intensely tive flame impinges end of the positive, made up in part of the incandescent surface of the end of the core 4 and in part of a portion 12 of the vapor issuing or flowing from the positive electrode. More specifically the spot referred to, when focused on the aperture plate of a p cture projector, was composed of iLSIIOW-Wllltfi center surrounded by a comparatively yellow concentric ring due to the incandescent shell of the positive carbon. It was further noted that a portion 13 of the positive flame eddied or swirled around as indicated in Fig. 1 which acted effectively, as the carbon 1 rotated, to round off the tip uniformly as indicated at 8. The are was found to be steady, of high efficiency compared to picture projecting arcs now in use, and the electrode consumption was no more rapid than that of the ordinary carbon arc. Referring to Fig. 2 it will be seen that the widest portion of the flame 9 was found to be at a position aa lying in a horizontal plane through the axis of the pos tive electrode 1. Certain other characteristics which distinguish my are from those inherent in other flaming arc projectors were noted and I wish to direct attention to them. The amount of spindling of the positive electrode was found to be about the same as that in the ordinary carbon arc. The negative tip assumed a form in which the core,

assumed a convex or outwardly bulged shape and the remainder of the tip a flat shape from which the negative flame 9 extended substantially at right angles as indicated in Fig. 1.

The positive vapor was not confined in any substantial degree to the positive crater but issued freely therefrom. The flames 9 and 10 swept upward and forwardly at an angle of about 20 with the vertical (the positive axis being horizontal) on the side towards the negative electrode. And to repeat for the sake of emphasis, the negative flame had no tongue nor did it touch the face or any other part of the positive electrode.

v By varying the dimensions, spacing of the electrodes, their relative angle, the current therethrough and other conditions I have been able to make obserr'ations leading to the following conclusions, among others;

The distance X between the point 11, where the two flames meet, and the positive crater face varies with the value of the arc current and the magnitude of the angle between the axes of the electrodes. Other thingsbeing equal, as the last mentioned angle increases the distance X.increase.. lVith the negative electrode at an angle 45 or less and with a current of 100 amperes or more the two flame effect is no longer evident but the negaupon the positive flame and confines the same substantially to the positi e crater as in the case of the high intensity are now extensively employed-in searchlights.

My novel are, which I term a two-flame arc,

creasing the consumption of the operates most satisfactorily when the carbons are placed at right angles but for reasons which will hereinafter appear I prefer to operate at a smaller angle.

I11 order to produce a two-flame are with carbons at a steep angle it is necessary to employ a cored positive electrode and preferably one in which the shell is quite large in crosssection as compared to that of the core. The core should be of such size and composition, for example a mixture of graphite and metallic salts or rare earths, that its linear consumption in operation will proceed at a rate sufliciently greater than that of its shell to produce a crateruof adequate depth, and so that suflicient vapor of great enough electrical conductivity will be generated in and emitted from the positive crater as to produce and maintain a steady arc. Under normal operating conditions the current of the arc is conducted to the positive flame or vapor stream by way of the core and also, to a limited extent, by way of the crater walls or carbon shell. With a core of the proper metallic impregnation and of the proper cross sectional area for a given diameter of shell a condition obtains where, as the core tends to burn away too rapidly, (i. e., the crater tends to become too deep)- more of the current is diverted through the shell to the flame inshell and-thus automatically maintaining the desired depth and shape of the crater. This diverting of the current must occur gradually and evenly, for should an appreciable amount of the arc current be suddenly shunted from the core to the shell the core would by virtue of its negative temperature coefficient of electrical resistance further reduce the current density at the core face and thus cause the crater to become almost black for an instant. This occurs where a core of too small a diameter is used. Furthermore a positive core of such size and composition should be employed as will produce a positive vapor stream of sufficientforce and volume, as to force and keep the negative flame away from crater face or tipof the positive electrode. The positive core should also have a low specific heat so that the greatest possible intrinsic brillianc of .the active core face maybe obtained. Moreover the positive core should have a greater negative temperature coeflicient of electrical resistance than its shell so as to provide a path of low resistance from the center of the electrode to centralize the crater on the tip of the carbon.

As stated above I have found certain flaming are carbons now in use in connection with A. C. flaming arcs to possess the characteristics above named.

One of the more important advantages of preventing the negative flame from touching the positive electrodemay be appreciated by considering what happens when this-0bjectionable'action is allowed to occur. Contact between the negative flame and positive electrode provides a current path of so much less resistance than that of the path from the positive vapor stream to-the negative flame that the most of the total current is conduct- I ed by way of the shell and the crater becomes almost black.

I prefer to operate my are at a current lying between the limits 25 and amperes, using the same diameter of shell and core for different current values but varying the composition of the core, i. e., the amount of impregnation with metallic salts. I also prefer to operate with the electrodes at an angle A between 45 and 95;

Because of its steadiness, comparatively low carbon consumption, and the intensity and whiteness of the light emitted by the small area positive core, my are is particularly adapted for motion picture projection. An illustration of my are so employed is indicated diagrammatically in Fig. 3. The positive electrode 1 is so controlled, as by means hereinafter disclosed, that the position of the active end of its core 4 is maintained at a substantially fixed distance from the condenser lenses 20, and substantially co-axial therewith. This distance is such that an image of the positive crater is formed at the aperture 21 of an aperture plate 22. Located adjacent the plate 22 111 any suitable film gate or other support is the film 23 or other image-bearing transparent member. The light passes through the aperture 21, through the film 23 and through a suitable optical system, comprising ob ectlve lenses 24, upon the screen.

As previously stated the light emitted by the core of the positive electrode is lntensely white while that of the surrounding crater shell is golden in col'or. To secure the best results in picture projection I prefer to screen out the golden ring which may be accomplished as follows: The focus is soad usted, i. e., the distance from crater to condenser 15 so regulated, that the image of the are at the aperture plate is sufliciently large to throw the golden ring of light from the carbon shell of the positive crater outside of the aperture 21 in the aperture plate. It will be noted that by virtue of the large angle A between the positive and negative electrodes the latter lies entirely outside of the cone of light between the positive core face and the objective.

In order to provide a practically successful projector lamp I provide means for auto matically accomplishing the following functions among others (1) To rotate the positive electrode in order to preserve a uniform crater,

(2) To feed the positive electrode as it is consumed to maintain the active face of the core 4 at the desired focal adjustment'above described,

23) To strike the are,

4) To feed the negative electrode. A preferred form of such means is illustrated in Figs. 4, 5 and 6, and may be constructed substantially as follows:

A. holder or support 30, adapted to be securedat 31 to the lamp or projector housing (not shown), is provided with a journal or bearing 32 within which a sleeve 33 is rotatably mounted and through which the electrode 1 extends. The sleeve 33 has a ratchet wheel 34 secured thereto on one side of said journal and a collar 35 is secured to said sleeve on the other side of said journal. The collar 35 carries a pair of brackets 36 at the ends of which gear wheels 37 are rotatably mounted. Each of the gears 37 meshes with a worm 38 whose shaft 39 is journaled in a boss 40 secured to the collar 35. The shaft 39 has secured thereto a pinion 41 which meshes with an internal gear 42 relatively rotatable with respect to the collar 35. The brackets 36 also pivotally support each of a pair of bell-crank levers 43 for oscillation about the axis of rotation of a corresponding one of gears 37. The bell cranks 43 carry gears 44 at their vertices which gears are rotatable with respect to the bell cranks and with respect to each other. The shafts 45, to. which the gears 44 are secured, have secured thereto feed rollers 46 which when revolved impart rotation to the electrode 1 and which when rotated impart a linear or feed movement to said electrode. A tension spring 47 connected at its opposite ends to the free ends of the bell cranks 43 serves to bias the rollers 46 into operative engagement with the electrode 1.

I prefer to constrain the internal gear 42 against rotation, as by means of an angle 48 suitably connected to said gear and the holder 30 for that purpose, so that on rotation of the ratchet wheel 34 the feed rollers will not only be revolved about the longitudinal axis of the electrode 1 but will be rotated about their own axes as well. By virtue of the above described mechanism it will be clearly understood that rotation of the ratchet wheel 34 in the proper direction will not only rotate the electrode 1 about its longitudinal axis but will impart a forward linear or feed movement thereto. I shall now proceed to describe the preferred mechanism for rotating the last mentioned ratchet wheeL' Directing attention to Fig. 5 as well as Fig. 4 it will be seen that the holder 30 has mounted thereon a plate 50. This plate is mounted for vertical, reciprocatory movement on said holder by means of a screw (51) and slot (52) connection and by virtue of its bifurcated lower end 53 which straddles the portion 56 of said plate and rotated by rotaand rotates the latter.

i holder 30.

tion of the shaft 57 journaled on said holder 30. I prefer to rotate the shaft 57 continuously, while the lamp "is in operation, by means of an electric motor 99 (not shown in Fig. 4 but indicated diagrammatically in Fig. 6). The plate has pivotally secured thereto at 59 a member 58 to which a pawl 60 is biased to a position in which it does not engage the ratchet 34 but if the pawl is moved to its other position it engages the ratchet The position of the pawl 60 and consequently the rotation and feed of the electrode 1 is controlled by an electromagnet 61, secured to the hol r 30, and whose pivotally mounted armature 62 carries a somewhat resilient arm 63 adapted to engage and operate the lower end of the pawl lever 60. Vhen the electromagnet 61 is energized the arm 63 throws the lower end of the pawl lever out and the upper-end into operative engagement with the ratchet 84:.

In order so to control the rotation and feed of the electrode 1 as to maintain a uniform positive crater at the desired focal position I provide a pair of auxiliary electrodes65, 66 which are carried by the holder but insulated therefrom and also insulated from each other. These electrodes are so positioned that when the crater is uniform and at the desired focal position the arc flame 10 does not engage and bridge them. When the consumption of the positive is of such a nature or to such an extent that the highly conductive arc flame 10 bridges said electrodes 65, G6. a highly conductive electrical path is established from one to the otherthereof. The auxiliary electrodes 65, 66 are preferably connected in series with a resistance and the coil 61, across the arc electrodes 1 and 2 as indicated diagrammatically in Fig. 6. Before proceeding with the description of the feed and rotation controlof the positive electrode I will now proceed to describe the structure by which the are is struck and by which the negative electrode 2 is fed to compensate for consumption.

A holder 70 for the negative electrode 2, and through which the latter is longitudinally movable. is hinged on or pivotally connected at '71 to a plate 72secured to but electrically insulated from the holder 30. The negative holder 70 is operatively connected at 73 to a rod 74: in turn secured to the core or plunger 75 of a solenoid 76 carried by the A compression spring 77. abutting at its opposite ends the yoke of the solenoid 7 6 and the plunger 75 serves to bias the holder 70 to a position in which the electrode 2 will engage and make electrical contact with the electrode 1. The position of the parts when the solenoid 76 is de-energized is illustrated in Fig. 4. Referring to Fig. 6 it will be seen that the arestriking solenoid 76 is connected in series with the arc and a resistance 7 8 across the line.

In order to feed the negative electrode 2 I provide one or more feed rollers 80, mounted for rotation on the holder 7 0 in a positionto engage and operate the electrode 2, said .roller or rollers being operatively connected a plurality of universal joints 83, one of which is shown in Fig. 4. The shaft 82 has secured thereto a pair of ratchet wheels 83; 84, the teeth on one of said wheels being oppositely directed with respect to the teeth on theother wheel (see Fig. 5). The plate 50 has pivotally connected thereto at 85 a pair of pawls 86 each adapted, at the to engage and operate a corresponding one of the ratchet wheels 83, 84. Obviously if the plate 50 is reeiprocated and either of the pawls 86 is operatively engaged with its corresponding ratchet wheel, the shaft 82 will be rotated in one direction or other, depending on which of the pawls is operatively associated with its ratchet. The pawls 86 may be controlled by means of the mechanism constructed substantially as follows.

A lever 88 is pivotally mounted at. 87 on the holder 30 or other suitable support and one of its arms constitutes the armature 89 of an electromagnet 90. The latter when energized exerts a pull on its armature in opposition to the tension spring 91. The other arm of the lever 88 has pivotally connected thereto an arm 92 which carries pairs of laterally projecting pins 93, 94, each of said pawls 86 extending between a corresponding pair of said'pins. When the pull of the solenoid 90 is sufficient to overcome the pull of the spring 91 the arm 92 is moved in a left hand direction and the left hand pawl 86 is thrown out of ratchet-engaging position (see Fig. 5). Vhen the pull of the spring 91 overcomes the pull of the electromagnet 90the reverse action takes place with respect to pawls 86. Referring to Fig. 6 it will be seen that the electromagnet 90 is connected across the arc electrodes 1 and 2.

Although the operation .of the form of invention illustrated will be clearly understood by those skilled in the art in view of the foregoing description it may be briefly summarized as follows.

Assume that the switch 100 is open and the electrodes 2 and 1 in contact with each other. -To start the lamp the switch 100 is closed. The solenoid 7 6 then becomes energized and, attracting its core, moves the parts to the position illustrated in Fig. 4 thereby separating the electrodes or striking the are. If the crater in the postive is of uniform shape and at the desired focal adjustment the arc flame does not bridge the electrodes 65 and 66 so that the electromagnet 61 is dead.

proper time,

crater. I

This means that the positive electrode 1 is neither being fed nor rotated even 'though the plate is being reciprocated by the motor 99, shaft 57 etc. If on the other hand the crater face has burned away at. its upper part so as to render the crater not uniform, or if the positive consumption has proceeded to such an extent that the crater is no longer at the desired focal adjustment, the arc flame 10 will engage and bridge the electrodes 65, 66. A circuit is then established through the electromagnet 61 to energize the same. The pawl 60 is consequently thrown to operative position and the reciprocation of the plate 50 causes the ratchet. 34 and therefore the positive electrode 1 to rotate about the longitudinal axis of the latter. The internal gear 42 being stationary the pinion 41-is rotated about its axis, due to its revolution about the axis of electrode 1, and a rotation is imparted to the feed rollers 46 to feed the electrode 1 forward. As soon as the flame 10 no longer bridges the electrodes 65, 66 the electromagnet 61 is de-energized and the above described rotation and feed ceases.

Before proceeding With the description of the operation I wish to call attention to an important and novel result obtained in the form of invention illustrated. As previously stated the purpose of rotating the electrode 1 is to maintain a uniform crater by avoiding lipping due to the action of the portion 13 of the arc flame upon the outer shell of the crater. It has been proposed to avoid lipping by continuously rotating the electrode 1 or by rotating the same intermittently but at regularly timed intervals (i. e., periodical- 1y). Neither of these methods completely solves the fproblem of maintaining a uniform extension of the crater face does form (and such is quite often the ease in practise) continuous or eriodic rotation does not remove this lip qu ckly enough, if at all. In my device, if a lip reaches-the uppermost point in its rotation it moves the'arc flame away from the electrodes 65 and 66 and stops rotation. And rotation will cease for a time commensurate with the extent of projection of the lip and until the lip is burned away. In other words the rotation is so controlled by the shape of the crater face as to maintain a uniform crater..

The operation of the negative electrode feed needs no very extended description. As

. the voltage supplied at the switch 100 is suberation .to feed or retract the electrode 2 through its holder to restore the arc to its proper length. In other words the electrofor any reason a lip or irregular The Wire in question is preferably connected to theholder 30 and a split collar or bushing (split on a vertical plane) employed to conduct the current from said holder to the electrode. Such a collar or bushing is indicated at 101 in Fig. 4. The bushing may be maintained in firm electrical contact with the electrode 1 by the construction illustrated in the last mentioned figure, which structure is constructed as follows.

A lever 102 is pivoted at 103 on one side of the holder 30 and its upper end engages the bushing through a suitable opening provided in the holder. A similar lever (not shown) is provided on the other side of the holder. These levers are biased into bushing-engaging position by means of a spring 104 whose arms each engage the lower ends of the levers to force the same outwardly or away from each other. Obviously the collar 101 and levers 102 are constructed of metal. Similar or other suitable means may be provided to convey current from the negative holder.

What I claim is 1. An arc lamp comprising in combination, an electrode, means including devices for conveying current to and from said electrode for producing a crater at the end thereof, means for rotating said electrode about its longitudinal axis, and means controlled by the shape of the face of the positive crater for stopping rotation for a length of time dependent upon the distance between the face and bottom of the crater at a predetermined portion of said crater.

2'. An arclamp comprising in combination, an electrode, means including devices forconveying current to and from said electrode for producing a' crater at the end thereof, means for rotatinsaid electrode about its longitudinal axis, and means controlled by the shape of the face of the positive crater for controlling said electrode-rotating means.

3. An arc lamp comprising in combination, an electrode, means including devices for conveying current to and from said electrode for producing a crater at the end thereof, means for rotating said electrode about its longitudinal axis, means for imparting a linear feed movement to said electrode whenever said electrode is rotated by said rotating means, and means controlled by the position and shape of said crater and in turn controlling form crater in a predetermined position.

4. An are lamp comprising in combination, a pair of feed rollers, means comprising gearsfor rotating each of said rollers in a direction opposite to that in which the other roller isrotating, and means whereb saidrollers may be moved toward and away 3 om each other to engage and disengage an electrode while maintaining the normal pitch relationship of said gears.

5. An are lamp comprising in combination, a plurality of feed rollers adapted to engage and feed an electrode, means comprising gears for rotating each of said rollers in a direction opposite tothat in which another of said rollers is rotating, means whereby said rollers may be moved toward and away from electrode-engaging position while maintaining the normal pitch relationship of said gears, and means for revolving said feed rollers about the axis of the electrode to rotate the latter.

6. A direct current are lamp comprising in combination, means for holding the positive and negative electrodes at an angle to expose the crater of the positive electrode, means for rotating the positive electrode about its longitudinal axis, and means'called into action by any lip formed upon the face of the crater of the positive electrode for suspending rotation of the positive electrode with the lip in the arc flame until the lip has burned away.

7. An arc lamp comprising in combination, an electrode, means including devices for conveying current to and fromsaid electrode for producing a, crater at the end thereof, means for rotating said electrode about its longitudinal axis, means for feeding said electrode in the direction of its longitudinal axis whenever it is rotated, and means controlled by the shape of the face of the positive crater for controlling said electrode rotating means, said fourth mentioned means including contacts adapted to be bridged by thearc flame sand instrumentalities controlled thereby to control the operation of said rotating means.

'8. The combination specified in claim 5 in which the first mentioned means comprises a pair of spur gears, and a worm gear in engagement with both of said spur gears for driving the same.

9. The combination specified in claim 5 in which the first mentioned means comprises a pair of spur gears and a Worm gear in engagement with both of said spur gears for driving the same, and in which resilient means are provided for biasing the feed rollers toward electrode-engaging position.

In testimony whereof I hereto aflix my signature.

EUGENE J. SCHAUB. 

